Prince Harry calls his mother the "naughtiest" princess in this early footage

A new documentary, Diana, Our Mother: Her Life and Legacy, airs in New Zealand this week and celebrates the life and work of Princess Diana in the 20th year since her tragic death.

The film marks the first time Princes William and Harry have spoken openly about their mother in a personal capacity, detailing fond childhood memories and the many ways she has shaped their adult lives.

And in a touching moment, Harry describes his mum as "the best mum in the world": "She was our mum. She still is our mum. And of course, as a son I would say this, she was the best mum in the world. She smothered us with love, that's for sure."

The documentary also reveals William's efforts to keep his mother's memory alive as he raises his own children and includes contributions and memoirs from the Princess' family and famous friends, several of whom have never spoken publicly about her before.

• This article was first published on nzherald.co.nz and is republished here with permission.